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Forum » SpaceEngine » General Discussions » Very extreme planet with life (Is this a bug?)
Very extreme planet with life
Tank7Date: Wednesday, 31.07.2013, 07:14 | Message # 1
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In 0.97 I have found this planet. Usually there is a hypothetical explanation for anything found in SE but I have doubts about this one.

Perhaps someone who is better prepared to crunch numbers could work out the density or weight of the atmosphere of this planet? I mean, is this planet's gravity even sufficient to hold the atmosphere together at such a high pressure? 7100+ atm...

And could any life as we know it including extremophillic microorganisms live here?

Moon RS 8404-1796-8-12725514-129 A5.3

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anonymousgamerDate: Wednesday, 31.07.2013, 08:20 | Message # 2
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I'm quite sure SE doesn't check atmospheric pressure when determining whether the planet has life or not. I've seen planets with life at the other end of the scale, with 0.005 atm.




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Tank7Date: Wednesday, 31.07.2013, 17:00 | Message # 3
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The other question I have though is like... ignoring the life detail, can an atmosphere of such pressure actually exist on a planet of this size? I could see such pressures deeper inside a gas giant but for this "super-earth" I would think the gravity is actually not sufficient for such a high atmospheric pressure to ever occur around a planet of this size & density. Again though I'm not prepared to truly prove it mathematically. Basically, I think if such a planet existed the atmosphere would "puff outwards" and be lost to the stellar wind, reducing the pressure. More realistically it would simply never become so dense in the first place during the formation stage.
 
apenpaapDate: Wednesday, 31.07.2013, 20:20 | Message # 4
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Well, Venus can hold 90 bars of atmosphere at a much higher temperature than this one, and this planet is five times heavier. I think it could probably hold that atmosphere. As for the life, I'm not sure if the pressure would truly be a problem for it, given that it evolved in it.




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Crashman1390Date: Wednesday, 31.07.2013, 20:55 | Message # 5
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I would not like to go there... Since the apparent CO^2 atmosphere, and the extreme jet lag, 51 days sheesh!




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Tank7Date: Wednesday, 07.08.2013, 22:12 | Message # 6
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Quote (apenpaap)
Well, Venus can hold 90 bars of atmosphere at a much higher temperature than this one, and this planet is five times heavier. I think it could probably hold that atmosphere. As for the life, I'm not sure if the pressure would truly be a problem for it, given that it evolved in it.


With the larger size though, the surface gravity is reported at 2.5G so then a Venusian atmospheric density, which I shall initially just "bump" to 100 bars, you get 250 bars.

However, I did get on Wikipedia, searched for "air" and found this:
Quote (Wikipedia)
The density of air at sea level is about 1.2 kg/m3 (1.2 g/L).

This translates to just 0.0012 grams per cubic centimeter.
Water is 1.0 grams per cm^3
Earth's average density is around 5.5 grams / cm^3
For this crazy planet, the density of air, 0.0012, multiplied by 7000 gives 8.4 grams / cm^3.
That means the atmosphere of this planet is more dense than iron, and more dense than most rocky planets. I doubt life would form here.

Also here is an excerpt from Wikipedia's page on Density
The values are given for Kg / m^3, so to convert to g / cm^3 you divide by 1000.

  • Zinc 7,000
  • Chromium 7,200
  • Manganese 7,325 Approx.
  • Tin 7,310
  • Iron 7,870
  • Niobium 8,570
  • Cadmium 8,650
  • Cobalt 8,900
  • Nickel 8,900
  • Copper 8,940


The atmosphere it's self would change the planet's average density, surface gravity, etc. considerably. Does SE take this into account? For an earth-like planet, or most desert/selena/titan the atmosphere is probably negligible when calculating the planet mass & surface gravity, but this iron/nickel density atmosphere would change things considerably.


Edited by Tank7 - Wednesday, 07.08.2013, 22:19
 
HarbingerDawnDate: Wednesday, 07.08.2013, 23:15 | Message # 7
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Quote (Tank7)
the surface gravity is reported at 2.5G so then a Venusian atmospheric density, which I shall initially just "bump" to 100 bars, you get 250 bars.

It doesn't work like that. How much of an atmosphere a planet can hold depends on the planet's mass, and the atmosphere's composition and temperature. Surface gravity is irrelevant. For example, Earth's moon has a higher surface gravity than Titan, yet Titan has an atmosphere thicker than Earth's while the Moon has none and would not be able to hold onto one if it somehow were given one.

Quote (Tank7)
For this crazy planet, the density of air, 0.0012, multiplied by 7000 gives 8.4 grams / cm^3

Again, it doesn't work like that. You can't just multiply the density of Earth's sea level air by the surface pressure of any atmosphere to get its density. For example, the atmosphere of Venus has a surface pressure 92 times that of Earth, but its air is only 56 times as dense. Mars' atmosphere is 0.006 times Earth's pressure, but 0.016 times its density, or a difference between pressure and density from Earth's by a factor of nearly 3. Obviously there's not a linear relationship there.

The density depends on a number of factors, including atmospheric composition, temperature, and pressure.





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WatsisnameDate: Wednesday, 07.08.2013, 23:41 | Message # 8
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The upper limit to atmospheric pressure is not simply a function of surface gravity. The most crucial requirement is that the velocity distribution of the molecules is less than the escape speed, so it depends on gravity, temperature, and composition. With 2.5g surface gravity and a temperature lower than Earth's, it could very easily support such a dense atmosphere.

Similarly, your air density calculation with this planet depends on more than just pressure. From the Ideal Gas Law, density is proportional to pressure and molar mass, and inversely proportional to temperature. (We've actually had a conversation on this, see it in General SE questions for more info). SE does not model atmospheric composition/density/etc at this time though, so don't take any of the numbers you get out of it too seriously. smile

edit: Gah, I should have refreshed before posting. :U





 
Tank7Date: Thursday, 08.08.2013, 02:08 | Message # 9
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Hmm thanks for the info guys. I still think this planet is a little ridicolous for life. The atmosphere is definetely extreme, even if you lower the density to 0.84 g / cm^3 (10% of that initial calculation) it's more like an ocean than an atmosphere smile

But it is very enlightening to see the info from both of you harbingerdawn and watsisname. Thanks again!
 
HarbingerDawnDate: Thursday, 08.08.2013, 03:02 | Message # 10
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Quote (Tank7)
it's more like an ocean than an atmosphere

Oceans have life, you know tongue High pressure is not much of an impediment to biology.





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